<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>Title</title>
</head>
<body>
<script>
    var i = 10;

    //这段代码，干扰了下面while语句中的变量
    for(var i = 0;i<100;i++){
        console.log(i);
    }

    while (i<20){
        console.log('我在while中，是第'+i);
        i++;
    }
</script>
</body>
</html>